The steadily increasing cost of electrical power predicates a greater attention to conservation and cost reduction in the operation of electrical appliances in industrial, commercial and residential sectors. There are many instances when electrical loads are left on to consume energy without there being a necessity for the loads being on. A typical example is when an individual enters a room in a residence, turns on the lights, spends a short time in the room and leaves without turning off the lights. Another example is in a commercial office building when users of offices and cleaning people leave the offices for the night with the lights remaining on.
Timers for electrical power control have been available but have tended to be mechanical devices with movable contacts, springs with encasements or pneumatic timing mechanisms. More recent timers for appliance and lamp control are either fully electronic, where timing and switching functions are handled by solid state devices or have electronic timing circuits which control an electromechanical power switching relay or contactor. Timers which are generally available are objectionable because of the noise that the timing and switching mechanism produces and, further, because of the cumbersome resetting required to keep the load activated for an extended period while still maintaining the automatic turn-off feature. Another disadvantage of available light timers is not generally appreciated: When used to control the main lights in spaces which would normally be dark without electrical light such as basements, attics, storerooms or other enclosed areas, a potential serious safety harzard is created. The control switch is normally remotely located--at the head of a stairway or adjacent to an entrance door--and immediate access to the timing switch is usually restricted. If the timer control times out before the occupant is ready to leave the illuminated area, and little or no auxillary lighting is available, the sudden onset of darkness could present a safety hazard. Even if ambient light is available, the inability to become darkadapted in a short period of time to the sudden loss of illumination constitutes a hazard and impairs mobility. By way of example, a light timer is ideal for turning off residential basement lights after the area is no longer occupied; however, the risk of losing illumination at an inappropriate time, such as when climbing stairs, etc., poses an unacceptable risk to the user.